Solid-state imaging sensor

ABSTRACT

The present technology relates to a solid state imaging sensor that is possible to suppress the reflection of incident light with a wide wavelength band. A reflectance adjusting layer is provided on the substrate in an incident direction of the incident light with respect to the substrate such as Si and configured to adjust reflection of the incident light on the substrate. The reflectance adjusting layer includes a first layer formed on the substrate and a second layer formed on the first layer. The first layer includes a concavo-convex structure provided on the substrate and a material which is filled into a concave portion of the concavo-convex structure and has a refractive index lower than that of the substrate, and the second layer includes a material having a refractive index lower than that of the first layer. It is possible to reduce the reflection on the substrate such as Si by using the principle of the interference of the thin film. Such a technology can be applied to solid state imaging sensors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase of International Patent Application No. PCT/JP2016/065024 filed on May. 20, 2016, which claims priority benefit of Japanese Patent Application No. JP 2015-114525 filed in the Japan Patent Office on Jun. 5, 2015. Each of the above-referenced applications is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present technology relates to a solid-state imaging sensor and, in particular, relates to a solid-state imaging sensor that can suppress the reflection of incident light with a wide wavelength band.

BACKGROUND ART

Small scale and multi-pixel are demanded to a solid-state imaging sensor. Therefore, reduction of pixels is developed. However, with the reduction of pixels, the sensitivity deteriorates, and thus it is demanded to compensate for the deterioration of sensitivity due to the reduction of an aperture ratio, and improve the sensitivity. In the solid-state imaging sensor, incident light is reflected on the surface of a Si substrate. Therefore, the intensity of light that reaches a light receiving portion is lost, and the sensitivity deteriorates, and the incident light from an unexpected light path causes flare and ghosts.

Accordingly, such a technology is proposed to effectively suppress the reflection of incident light on all wavelength regions (all visible light) of the incident light on a light receiving portion by forming a reflection preventing layer having a concavo-convex structure (also referred to as a moth-eye structure) corresponding to a wavelength region of incident light on the light receiving portion (refer to, e.g., Patent Literature 1).

CITATION LIST Patent Literature

Patent Literature 1: JP2009-218357A

DISCLOSURE OF INVENTION Technical Problem

Incidentally, in the case of using the moth-eye structure adopted in Patent Literature 1 described above, a deep concavo-convex structure with a narrow pitch is required. However, the level of difficulty is technically high to realize the structure with thickness less than, e.g., approximately 100 nm by processing, such as lithography or dry etching.

Further, in the case of using the moth-eye structure, as long as the thickness of at least approximately 100 nm is not ensured, the reflectance cannot be sufficiently reduced.

The present technology is devised under the situation. In particular, the interference principle of a thin film is applied to the surface of a Si substrate, thereby suppressing the reflection of incident light with a wide wavelength band.

Solution to Problem

According to an aspect of the present technology, a solid-state imaging sensor is a solid-state imaging sensor including: a substrate having, per pixel unit, a photoelectric conversion unit configured to generate a pixel signal corresponding to an amount of incident light by photoelectric conversion; a reflectance adjusting layer provided on the substrate in an incident direction of the incident light with respect to the substrate and configured to adjust reflection of the incident light on the substrate; and an environmental medium provided on the reflectance adjusting layer. The reflectance adjusting layer includes a first layer formed on the substrate and a second layer formed on the first layer. The first layer includes a concavo-convex structure provided on the substrate and a material which is filled into a concave portion of the concavo-convex structure and has a refractive index lower than that of the substrate. The second layer includes a material having a refractive index lower than that of the first layer. The refractive index of the substrate is higher than that of the first layer, the refractive index of the first layer is higher than that of the second layer, and the refractive index of the second layer is higher than that of the environmental medium.

A product of the refractive index of the first layer and a thickness of the first layer may be smaller than ⅜ times a wavelength of the incident light.

The first layer may include a plurality of layers, and in a refractive index of each of the plurality of layers, and the refractive index of a layer closer to the substrate may be higher among any adjacent layers. In the case where a difference in the refractive index between the respective layers is higher than a predetermined value, a product of the refractive index and the thickness may be smaller than ⅜ times the wavelength of the incident light in each of the plurality of layers. In the case where the difference in the refractive indexes between the respective layers is lower than a predetermined value, a sum of products of the refractive index and the thickness of each of the plurality of layers may be smaller than ⅜ times the wavelength of the incident light.

A product of the refractive index of the second layer and a thickness of the second layer may be smaller than ⅜ times the wavelength of the incident light.

The second layer may include a plurality of layers, and in a refractive index of each of the plurality of layers, the refractive index of a layer closer to the substrate may be higher among any adjacent layers. In the case where a difference in the refractive index between the respective layers is higher than a predetermined value, a product of the refractive index and the thickness may be smaller than ⅜ times the wavelength of the incident light in each of the plurality of layers. In the case where the difference in the refractive indexes between the respective layers is lower than a predetermined value, a sum of products of the refractive index and the thickness of each of the plurality of layers may be smaller than ⅜ times the wavelength of the incident light.

The refractive index of the first layer may be a sum of products of volume ratios with the respective refractive indexes of a convex portion in the concavo-convex structure of the first layer including the same material as that of the substrate and the concave portion to which the material with the low refractive index is filled.

The substrate includes Si and InGaAs, a material filled into a concave portion of the first layer may include an oxidized film or a nitride film containing at least one kind of Hf, Al, Ti, Zr, Ta, Nb, Y, and Sr, and the environmental medium may include a lens, a color filter, and an oxidized film.

A material filled into the concave portion of the first layer may include SiN, HfO2, Ta2O5, Nb2O5, TiO2, Al2O3, and ZrO2.

A material filled into the concave portion of the first layer may be the same material as that of the second layer.

A material filled into the concave portion of the first layer may be the material with high dielectric constant.

The concavo-convex structure provided on the substrate may be configured by using photolithography or etching using directed self assembly (DSA).

A boundary per the pixel unit may include an oxidized-film boundary portion including an oxidized film.

The pixel may include an image-plane phase difference focus pixel.

A boundary per the pixel unit may include a metallic boundary portion including a metal.

The metal may include tungsten.

The pixel may include an image-plane phase difference focus pixel.

The solid-state imaging sensor may include a light shielding unit which is the boundary per the pixel unit and which includes the same metal as that of the metallic boundary portion and shields the incident light onto an adjacent pixel to surround the pixel in a direction facing to an incident direction of the incident light.

The pixel may include an image-plane phase difference focus pixel.

According to an aspect of the present disclosure, a solid-state imaging sensor includes: a substrate having, per pixel unit, a photoelectric conversion unit configured to generate a pixel signal corresponding to an amount of incident light by photoelectric conversion; a reflectance adjusting layer provided on the substrate in an incident direction of the incident light with respect to the substrate and configured to adjust reflection of the incident light on the substrate; and an environmental medium provided on the reflectance adjusting layer. The reflectance adjusting layer includes a first layer formed on the substrate and a second layer formed on the first layer. The first layer includes a concavo-convex structure provided on the substrate and a material which is filled into a concave portion of the concavo-convex structure and has a refractive index lower than that of the substrate. The second layer includes a material having a refractive index lower than that of the first layer. The refractive index of the substrate is higher than that of the first layer, the refractive index of the first layer is higher than that of the second layer, and the refractive index of the second layer is higher than that of the environmental medium.

Advantageous Effects of Invention

According to an aspect of the present technology, it is possible to suppress the reflection of incident light with a wide wavelength band.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration example of a first embodiment of a solid-state imaging sensor to which the present technology is applied.

FIG. 2 is a diagram illustrating a configuration for reducing the reflection from a Si substrate in the solid-state imaging sensor in FIG. 1.

FIG. 3 is a perspective view illustrating the configuration in FIG. 2.

FIG. 4 is a flowchart illustrating a manufacturing method of the configuration in FIG. 2 of the solid-state imaging sensor in FIG. 1.

FIG. 5 is a diagram illustrating a conventional relation between a wavelength of incident light and the reflectance.

FIG. 6 is a diagram illustrating a relation between the wavelength of incident light and the reflectance when the configuration in FIG. 2 is used.

FIG. 7 is a diagram illustrating a configuration example of a second embodiment of a solid-state imaging sensor to which the present technology is applied.

FIG. 8 is a diagram illustrating a configuration example of a third embodiment of a solid-state imaging sensor to which the present technology is applied.

FIG. 9 is a diagram illustrating a relation between a wavelength of incident light and the reflectance when using a configuration for reducing the reflection from a Si substrate in the solid-state imaging sensor in FIG. 8.

FIG. 10 is a diagram illustrating a configuration example of a fourth embodiment of a solid-state imaging sensor to which the present technology is applied.

FIG. 11 is a diagram illustrating a relation between a wavelength of incident light and the reflectance when using the configuration for reducing the reflection from a Si substrate in the solid-state imaging sensor in FIG. 10.

FIG. 12 is a diagram illustrating a configuration example of a fifth embodiment of a solid-state imaging sensor to which the present technology is applied.

FIG. 13 is a diagram illustrating a first modification of the fifth embodiment of the solid-state imaging sensor to which the present technology is applied.

FIG. 14 is a diagram illustrating a configuration example of a sixth embodiment of a solid-state imaging sensor to which the present technology is applied.

FIG. 15 is a diagram illustrating a first modification of the sixth embodiment of the solid-state imaging sensor to which the present technology is applied.

FIG. 16 is a diagram illustrating a second modification of the sixth embodiment of the solid-state imaging sensor to which the present technology is applied.

FIG. 17 is a diagram illustrating a third modification of the sixth embodiment of the solid-state imaging sensor to which the present technology is applied.

FIG. 18 is a schematic diagram illustrating an application example of an electronic device to which the solid-state imaging sensor according to the present technology is applied.

FIG. 19 is a diagram illustrating use examples of a solid-state imaging sensor according to the present technology.

MODE(S) FOR CARRYING OUT THE INVENTION

<First Embodiment>

<Configuration Example of Embodiment of Solid-State Imaging Sensor to Which the Present Technology is Applied>

FIG. 1 is a sectional side view illustrating a configuration example of an embodiment of a solid-state imaging sensor to which the present technology is applied.

A solid-state imaging sensor 11 in FIG. 1 includes, from the top in the diagram, a lens 31, a color filter 32, a planarized film 33, a light shielding film 34, an oxidized film (SiO2) 35, an intermediate second layer 36, an intermediate first layer 37, and a Si substrate 38.

The solid-state imaging sensor 11 in FIG. 1 receives light incident from the top in the diagram to generate a pixel signal corresponding to the amount of received light.

More specifically, the lens 31 collects incident light on a photoelectric conversion element (not shown) provided per pixel unit in the Si substrate 38. Note that, in the diagram, a convex portion toward the top in the diagram in the lens 31 corresponds to each pixel. In FIG. 1, three pixels are arranged in the horizontal direction as an example.

The color filter 32 is a filter through which only light with a specific wavelength is transmitted of the incident light, for example, extracts light with a wavelength corresponding to any of RGB (red, green, blue), and allows the light to be transmitted through a post-stage configuration.

The planarized film 33 allows the color filter 32 and the oxidized film 35 to be adhered and connected to each other.

The light shielding film 34 includes a metallic film, such as W (tungsten), for example, to shield the incident light onto an adjacent pixel and prevent the crosstalk of the incident light between pixels.

The oxidized film 35 electrically isolates between adjacent pixels to prevent the crosstalk of a pixel signal between the adjacent pixels. In particular, a boundary portion 35 a including the same material as that of the oxidized film 35 provided to a trench provided in the boundary between the respective pixels is formed to prevent the leakage of the pixel signal to pixels adjacent in the horizontal direction. Note that, the lens 31, the color filter 32, the planarized film 33, the light shielding film 34, and the oxidized film 35 are generically referred to as environmental media or environmental medium layers, for the subsequent configuration.

The two layers of the intermediate first layer 37 and the intermediate second layer 36 form an intermediate layer having a pseudo high-refracting layer, and function as reflectance adjusting layers for suppressing the reflection on the Si substrate 38. Herein, the intermediate second layer 36 includes a boundary portion 36 a which has the same material as that of the oxidized film 35 and surrounds the boundary portion 35 a provided at the boundary per pixel unit. The respective pixels are electrically isolated by the boundary portion 35 a and the crosstalk of the pixel signal between adjacent pixels is suppressed.

More specifically, the reflectance adjusting layer with a structure for suppressing the reflection of the incident light shown within a range surrounded by a dotted line in FIG. 1 has a configuration illustrated in FIG. 2.

FIG. 2 is a diagram illustrating the configuration of the reflectance adjusting layer surrounded by a dotted line part in the solid-state imaging sensor 11 in FIG. 1 to suppress the reflection of the incident light. In FIG. 2, from the top, the oxidized film 35, the intermediate second layer 36, the intermediate first layer 37, and the Si substrate 38 are provided. Among those, the intermediate second layer 36 and the intermediate first layer 37 function as reflectance adjusting layers.

The intermediate second layer 36 is formed of a material, for example, SiN, HfO2, Ta2O5, Nb2O5, and TiO2 with a refractive index n2 ranging from 1.9 to 2.3.

Further, the intermediate first layer 37 is configured by mixedly arranging, for example, a material forming the intermediate second layer 36 and a material Si forming the Si substrate 38. More specifically, as illustrated in FIG. 3, a concavo-convex structure is formed on the Si substrate 38. The material forming the intermediate second layer 36 is filled into a concave portion 37 a of the structure. Note that, in FIG. 3, a material forming the intermediate second layer 36 is filled into the concave portion 37 a, thereby forming a prismatic shape to be provided in the concave portion 37 a in the concavo-convex structure on the Si substrate 38. Herein, the structure formed in the concave portion 37 a is not limited to the prismatic shape, but may be another shape, for example, cylinder shape. Further, the intermediate first layer 37 has a height d1 of the concave portion 37 a within a range of approximately 20 to 60 nm, and is configured by mixedly arranging a material forming the Si substrate 38 and a material forming the intermediate second layer 36 with a volume ratio thereof as a predetermined value. Consequently, a refractive index n1 of the intermediate first layer 37 is 2.6 to 3.7 as a whole.

More specifically, the intermediate first layer 37 ideally includes a material with an extinction coefficient as 0 and a refractive index ranging from 2.6 to 3.7. However, there is not actually the material with the extinction coefficient as 0 and the refractive index ranging from 2.6 to 3.7. Therefore, the intermediate first layer 37 is formed by mixedly arranging a material forming the Si substrate 38 with a refractive index ns=4.1 and a refractive index adjusting material (herein, the same material as that forming the intermediate second layer 36) with the refractive index n2 ranging from 1.9 to 2.3 lower than the refractive index of the Si substrate with a volume ratio thereof. As a whole, the refractive index is averaged and the refractive index n1 ranges from 2.6 to 3.7.

For example, in a case where a volume V1 of the concave portion 37 a forming the intermediate first layer 37 and a volume V2 with the same range as that of the material of the Si substrate 38 (convex portion to the concave portion 37 a) satisfy a relation of V1:V2=3:2, when the refractive index ns of the material Si of the Si substrate 38 is 4.1 and a material forming the intermediate second layer 36 is Ta2O5 with the refractive index n2 as 2.2, the intermediate first layer 37 is formed with the refractive index n1 as approximately 3.3 that is averaged by mixed arrangement corresponding to the volume ratio thereof.

However, when a refractive index n1 of the oxidized film 35 containing SiO2 is 1.46 and the refractive index ns of the Si substrate 38 is 4.1, if the refractive index n1<refractive index n2<refractive index n1<refractive index ns is satisfied, the intermediate first layer 37 and the intermediate second layer 36 may be formed of a material with another refractive index. Note that, for the Si substrate 38, a substrate containing InGaAs with the refractive index as approximately 4.0 can be similarly used.

<Manufacturing Method>

Next, a description will be given of a manufacturing method of a reflectance adjusting layer including the oxidized film 35, the intermediate second layer 36, the intermediate first layer 37, and the Si substrate 38, and having a structure surrounded by the dotted line in FIG. 1 for reducing the reflectance, with reference to a flowchart of FIG. 4.

In step S11, within a range of formation of the intermediate first layer 37 on the Si substrate 38 including a photoelectric conversion element (not shown), for example, with photolithography, the concave portion 37 a is formed with a predetermined pitch p1, a width w1, and a height (depth) d1. Herein, the concave portion 37 a illustrated in FIGS. 2 and 3 has a prismatic shaped configuration with, for example, the height (depth) d1 of 31 nm, width w1 of 57 nm, and pitch p1 of 90 nm. Therefore, a convex portion on which Si of the Si substrate 38 remains has the width of 33 nm. A volume ratio of V1 to V2 is, for example, 3:2 where the volume V1 is formed of Si forming the Si substrate 38 and the volume V2 is a volume of the concave portion 37 a with the configuration.

Note that the pitch is preferably the wavelength or less of the adjacent intermediate second layer 36. Therefore, for example, when the shortest wavelength is 400 nm and the refractive index of the intermediate second layer 36 is 2.2, the pitch p1 is preferably a wavelength λ2 (=182 nm=400/2.2) or less in the intermediate second layer 36. Further, the height d1 of the concave portion 37 a has an ideal condition (n1×d1=λ/4) that 2×refractive index (n1)×height (d1) is a half wavelength (λ/2) in the reciprocating light path of the light in the thin film with interference of the thin film. However, since there is a degree of freedom for adjusting the refractive index and the height to the intermediate second layer 36, the condition may be within a range of n1×d1<3λ/8. That is, the height d1 is 31 nm, smaller than 62.5 (=3×550/8/3.3) nm.

In step S12, the intermediate first layer 37 is formed by filling the refractive index adjusting material into the concave portion 37 a. In the example in FIG. 2, the refractive index adjusting material has the same material as that of the intermediate second layer 36. For example, when the incident light is light of 550 nm, the intermediate first layer 37 is formed by filling Ta2O5 with the refractive index n2 as 2.2.

In step S13, the intermediate second layer 36 is formed. That is, in FIG. 2, when the same incident light as that of the refractive index adjusting material is light of 550 nm, the film is formed with lamination so that the height d2 of Nb2O5 with the refractive index n2 as 2.2 is 54 nm.

In step S14, chemical mechanical polishing (CMP) is applied to the top surface of the intermediate second layer 36, thereby flattening the unevenness corresponding to the unevenness on the top surface of the intermediate first layer 37. For example, in FIG. 2, the height d2 of the intermediate second layer 36 is set to 54 nm. That is, the height d2 of the intermediate second layer 36 has an ideal condition (n2×d2=λ/4) that 2×refractive index (n2)×height (d2) is a half wavelength (λ/2) in the reciprocating light path of the light in the thin film with interference of the thin film. However, there is a degree of freedom for adjusting the refractive index and height to the intermediate first layer 37, the condition may be within a range of n2×d2<3λ/8. That is, the height d2 is 54 nm smaller than 93.8 (=3×550/8/2.2) nm.

Note that, the flattening may be used. Therefore, the processing may be processing except for the CMP, for example, the flattening may be performed by using etching. Further, since effects can be obtained although the improvement effect deteriorates in the case of omitting CMP, CMP may be omitted.

In step S15, the oxidized film 35 containing SiO2 is formed and, subsequently, the components including the oxidized film 35 and above in FIG. 1 are formed as an environmental medium layer.

With the configuration manufactured by the processing, for example, in FIG. 2, in the intermediate first layer 37 as a whole, the refractive index n1 is 3.3, and it is possible to suppress the reflection from the Si substrate 38 as a whole.

Herein, conditions with the above processing are marshaled.

The refractive index n1 is expressed by the following Formula (1) using the refractive index ns of Si in the Si substrate 38 and the refractive index n2 of the refractive index adjusting material with the same material in the intermediate second layer 36. n1=ns×rs+r2×n2  (1)

In Formula (1), rs and r2 denote weight coefficients obtained by a ratio of volume V1 made of Si forming the Si substrate 38 in the intermediate first layer 37 to volume V2 of the concave portion 37 a, V1:V2=rs:r2 and rs+r2=1 are obtained.

When a wavelength of transmitted light is λ, a relation between height (depth) d1 of the intermediate first layer 37 and the refractive index n1 of the intermediate first layer 37 is generalized and expressed by the following Formula (2). n1×d1<3λ/8  (2)

Herein, the basis of Formula (2) is obtained from a relation between the wavelength and the difference in reciprocating light path with the interference of the thin film. However, a condition for reducing the reflectance most in the interference of the thin film is set when a relation is established with an offset of a half-wavelength phase represented by the following Formula (3). n1×d1=λ/4  (3)

However, also in the intermediate second layer 36, the similar interference operation can be expected. Therefore, it is when the relation of Formula (2) described above is satisfied in consideration of the degree of freedom caused by combination with the refractive index n2 and height d2 of the intermediate second layer 36.

Similarly, when a wavelength of transmitted light is λ, a relation between the height d2 and the refractive index n2 of the intermediate second layer 36 is generalized and expressed by the following Formula (4). n2×d2<3λ/8  (4)

Also here, the basis of Formula (4) is obtained from a relation between the wavelength and the difference in reciprocating light path with the interference of the thin film. However, a condition for reducing the reflectance most in the interference of the thin film is set when a relation is established with an offset of a half-wavelength phase represented in the following Formula (5). n2×d2=λ/4  (5)

However, also in the intermediate first layer 37, the similar interference operation can be expected. Therefore, it is when the relation of Formula (4) is satisfied in consideration of the degree of freedom caused by combination with the refractive index n1 and height d1 of the intermediate first layer 37.

That is, to summarize the above conditions, as a first condition, when the refractive indexes of the Si substrate 38, the intermediate first layer 37, the intermediate second layer 36, and the oxidized film 35 are ns, n1, n2, and n1, respectively, the following Formula (6) is satisfied, and the conditions of Formula (2) and Formula (4) described above are satisfied, it is possible to reduce the reflection of incident light transmitted via the lens 31 and the color filter 32 on the Si substrate 38 by using the principle of the interference of the thin film. ns>n1>n2>ni  (6)

Herein, the mechanism for reducing the reflection on the Si substrate 38 is not a mechanism for reducing the reflection with stepwise refraction using the thickness like the moth eye, but a mechanism for reducing the reflectance by applying the operation of the interference of the thin film with a plurality of films. Therefore, a thinner configuration than that of the moth eye enables the reduction of the reflection from the Si substrate 38.

Further, normally, in the case of using only the thin film with the refractive index of 1.9 to 2.4 to which incident light with a central wavelength of 550 nm is assumed, as illustrated in FIG. 5, when the reflectance is measured with replacement of the wavelength of the incident light, the reflectance is approximately 1.5 in the case of light with a peripheral wavelength of 550 nm as the central wavelength. However, in the case of incident light with a wavelength band other than the central wavelength, the reflectance has a value exceeding 2 as a whole.

However, with the solid-state imaging sensor, as illustrated in FIG. 6 to which the present technology is applied, the reflectance can be set to approximately 1 as a whole with a wide wavelength band of 400 nm to 700 nm. It is possible to reduce the reflectance of the incident light with a wide wavelength band.

As a result, it is possible to suppress the reflection on the Si substrate 38 of the solid-state imaging sensor 11. Further, it is possible to suppress the reduction of the sensitivity in the photoelectric conversion element, and the light is not incident on adjacent pixels. Therefore, flare and ghosts can be reduced. Further, unlike the moth eye, with the configuration obtained by applying the effect of the interference of the thin film, the reflection on the Si substrate 38 can be suppressed. Therefore, it is possible to realize a reflectance adjusting layer that suppresses the reflection with a thinner configuration than the configuration to suppress the reflection by using the moth eye, for example, a configuration thinner than 100 nm.

Note that, with the configuration of the concave portion 37, it is possible to substantially ignore the influence from a taper (change of up to an area ratio of approximately 0.2), smooth bases at top and bottom ends of the unevenness, and roughness.

Further, in the processing in step S11, the example of using photolithography is described when the concave portion 37 a is provided, but as long as the volume ratio is realized, another method may be used. For example, by using directed self assembly (DSA), the volume of Si as a material of the Si substrate 38 and the volume of the concave portion 37 a have the volume ratio. With etching, the concave portion 37 a may be formed.

Furthermore, even in the case where a layer with a refractive index nia and a height dia is formed between any layers and a relation of nia×dia<λ/2 is satisfied, if the difference in refractive index between adjacent layers is approximately 10 percent, the influence is small. Therefore, the configuration may be considered as that included in continuous layers.

Further, when a layer with the refractive index nia and the height dia is formed between any layers and ni2×di2<λ/10 is satisfied, the thickness of the inserted layer is considered to be extremely thin. Therefore, it is assumed that there is not the influence from the interference, and the layer may be ignored. For example, even if there is a high-refractive-index layer of approximately n=2.2 containing Nb2O5 or the like, the height as the film thickness is sufficiently thin, such as 5 nm, the influence may be ignored. Further, even if there is a plurality of layers under the above-described conditions, the layer can be similarly handled.

<Second Embodiment>

In the foregoing, the example has been given of using the same material as that used in the intermediate second layer 36 as the refractive index adjusting material filled into the concave portion 37 a in the intermediate first layer 37. As mentioned above, if the conditions in Formula (2), Formula (4), and Formula (6) described above are satisfied, the refractive index adjusting material may be different from the material used in the intermediate second layer 36.

That is, for example, as illustrated in FIG. 7, the Al2O3 with the refractive index of 1.6 may be filled into a cylindrical-shaped concave portion 37 a′ corresponding to the concave portion 37 a.

In this case, the volume ratio of Si to Al2O3 in the intermediate first layer 37 is 67:33. Therefore, both weight coefficients rs and rAl2O3 are 0.67 and 0.33, respectively.

As a consequence thereof, the height d12 of the intermediate first layer 37 is, e.g., 31 nm, the height d11 of the intermediate second layer 36 is, e.g., 54 nm, the pitch p11 of the cylindrical-shaped concave portion 37 a′ is, e.g., 90 nm, and the width (diameter) w12 of the cylindrical-shaped concave portion 37 a′ is, e.g., 59 nm.

Thus, the intermediate first layer 37 having the concave portion 37 a′ into which Al2O3 is filled is formed on the Si substrate 38. Note that, if the refractive index n1 and height d1 of the intermediate first layer 37 have thickness of n1×d1<λ/10 or less, it is assumed that there is substantially not the influence from the interference. Therefore, the polishing is not necessarily required with the CMP till the convex portion is exposed from the Si substrate 38 in the intermediate first layer 37, and Al2O3 filled into the concave portion 37′ may remain with approximately 10 nm.

Further, as the refractive index adjusting material filled into the concave portion 37 a in the intermediate first layer 37, as long as the conditions in Formula (2), Formula (4), and Formula (6) described above are satisfied, another material may be used, for example, an oxidized film or a nitride film including at least one kind of Hf, Al, Ti, Zr, Ta, Nb, Y, and Sr, for example, ZrO2.

With the configuration, the similar effect to that of the configuration in FIG. 2 can be obtained.

Further, by using a material with a high dielectric constant called a high-k material, such as Al2O3 to the top of the Si substrate 38, the protection by dry etching is possible from a damage when processing the Si substrate 38. Further, it is possible to protect an interface state by a film containing Al2O3 or the like having fixed charges.

<Third Embodiment>

In the foregoing, the description has been given of the example in which the intermediate first layer 37 includes 1 layer, but the intermediate first layer 37 may include a plurality of layers.

That is, for example, as illustrated in FIG. 8, the intermediate first layer 37 may include 2 layers of intermediate first layers 37-1 and 37-2.

In FIG. 8, the intermediate first layer 37 includes 2 layers of the intermediate first layers 37-1 and 37-2. In the intermediate first layer 37-1, a concave portion 37 a-1 has a pitch p11, a height d11-1, and a width w11-1. The intermediate first layer 37-2 includes the concave portion 37 a-2 having the pitch p11, a height d11-2, and a width w11-2.

In this case, the condition is changed depending on the relation of the refractive indexes of the respective layers. First, when the refractive indexes of the intermediate first layers 37-1 and 37-2 are n11 and n12 respectively, the relation of the refractive indexes of the layers preferably satisfies the following relation in Formula (7), corresponding to the relation in Formula (6) described above. ns>n11>n12>n2>ni  (7)

Further, the difference in refractive index between the intermediate first layers 37-1 and 37-2 is larger than a predetermined value (e.g., difference (ns−n11) between the refractive index of the Si substrate 38 and the refractive index of the intermediate first layer 37-1) (n11−n12>ns−n11), the effect of the interference is assumed to be large in the respective intermediate first layers 37-1 and 37-2. In each of the intermediate first layers 37-1 and 37-2, the relation in Formula (2) is satisfied.

On the other hand, when the difference in refractive index between the intermediate first layers 37-1 and 37-2 is smaller than a predetermined value (e.g., difference (ns−n11) between the refractive index of the Si substrate 38 and the refractive index of the intermediate first layer 37-1) (n11−n12<ns−n11), the effect of the interference is assumed to be small in the respective intermediate first layers 37-1 and 37-2. Therefore, the intermediate first layers 37-1 and 37-2 are assumed to be the same layer together, and the following relation in Formula (8) is satisfied. n11×d11-1+n12×d11-2+ . . . <3λ/8  (8)

Note that Formula (8) includes the case in which the intermediate first layer 37 includes 3 layers or more. In this case, the refractive index of the third layer or subsequent layer is n13, n14 . . . . Each height is d11-3, d11-4 . . . . In FIG. 8, the intermediate first layer 37 includes 2 layers, and Formula (8) is therefore expressed by “n11×d11-1+n12×d11-2<3λ/8”.

As an example in which the difference in refractive index between the intermediate first layers 37-1 and 37-2 is larger than a predetermined value (n11−n12>ns−n11) and the condition in Formula (2) is satisfied, for example, if the refractive indexes of the intermediate first layers 37-1 and 37-2 are n11=3.7 and n12=3.1, respectively, d11-1=37 nm and d11-2=34 nm are obtained. When the refractive index adjusting material is Nb2O5 (refractive index 2.2), the concave portions 37 a-1 and 37 a-2 are structured to be quadratic-prism-shaped to satisfy the refractive indexes n11 and n12 of the intermediate first layers 37-1 and 37-2. The pitch p11 is 90 nm. Regarding the width, the width w11-1 is equal to 42 nm and the width w11-2 is equal to 65 nm, respectively.

With the configuration, for example, as illustrated in FIG. 9, the reflectance from the Si substrate 38 can be set to 2 or less at a wide wavelength band ranging from 400 nm to 800 nm of incident light. In particular, when the wavelength λ ranges from 500 to 520 nm, the reflectance can be set to approximately 0.

<Fourth Embodiment>

In the foregoing, the example has been given that the intermediate first layer 37 includes a plurality of layers. Similarly, the intermediate second layer 36 may include a plurality of layers.

That is, for example, as illustrated in FIG. 10, the intermediate second layer 36 may include 2 layers of intermediate second layers 36-1 and 36-2.

In FIG. 10, the intermediate second layer 36 includes 2 layers of the intermediate second layers 36-1 and 36-2, the intermediate second layer 36-1 contains, for example, Nb2O5 (refractive index 2.2) with a height d12-1, and the intermediate second layer 36-2 contains Ao2O3 (refractive index 1.65) with a height d12-2.

Note that, regarding the intermediate first layer 37, the concave portion 37 a is formed with a height d11, a width d11, and a pitch p11.

In this case, the condition is changed depending on the relation of the refractive indexes between the layers. First, if the refractive indexes of the intermediate second layers 36-1 and 36-2 are n21 and n22, respectively, the relation of the refractive indexes between the respective layers preferably satisfies the following relation in Formula (9), corresponding to the relation in Formula (6) described above. ns>n1>n21>n22>ni  (9)

Further, when the difference (n21−n22) in refractive index between the intermediate second layers 36-1 and 36-2 is larger than a predetermined value (e.g., difference (n22−ni) between the refractive index of the oxidized film 35 and the refractive index of the intermediate second layer 36-2) (n21−n22>n22−ni), the effect of the interference is assume to be large in the respective intermediate second layers 36-1 and 36-2. Therefore, the relation of Formula (4) is satisfied in the respective intermediate second layers 36-1 and 36-2.

On the other hand, when the difference (n21−n22) in refractive index between the intermediate second layers 36-1 and 36-2 is smaller than a predetermined value (e.g., difference (n22−ni) between the refractive index of the oxidized film 35 and the refractive index of the intermediate second layer 36-2) (n21−n22<n22−ni), the effect of the interference is assumed to be small in the respective intermediate second layers 36-1 and 36-2. Therefore, the intermediate second layers 36-1 and 36-2 are assumed to be the same layer together, the following relation of Formula (10) is satisfied. n21×d12-1+n22×d12-2+ . . . <3λ/8  (10)

Note that Formula (10) includes a case where the intermediate second layer 36 includes 3 layers or more. In this case, the refractive index of the third layer or subsequent layer is n23, n24 . . . . Each height is d12-3 and d12-4 . . . . In FIG. 10, an example of a configuration of 2 layers is represented. Therefore, Formula (10) is “n21×d12-1+n22×d12-2<3λ/8”.

As an example in which the difference (n21−n22) in refractive index between the intermediate second layers 36-1 and 36-2 is larger than a predetermined value (n21−n22>n22−ni) and the condition of Formula (4) is satisfied, for example, when the refractive indexes of the intermediate second layers 36-1 and 36-2 are n21=2.2 and n22=1.65, respectively, the heights d12−1=58 nm and d12−2=55 nm are obtained. When the refractive index adjusting material is Nb2O5 (refractive index 2.2), the concave portion 37 a is structured to be quadratic prism so as to satisfy the refractive index n11 of the intermediate first layer 37. The pitch p11 is 90 nm, the height d11 is 34 nm, and the width w11 is 57 nm.

With the configuration, for example, as illustrated in FIG. 11, at a wide wavelength band of 400 nm to 800 nm of the incident light, the reflectance from the Si substrate 38 can be set to 1.5 or less. In particular, at a wavelength λ of 430 nm and 700 nm, the reflectance can be set to approximately 0.

<Fifth Embodiment>

In the foregoing, as illustrated in FIG. 1, the description has been given of the example in which the crosstalk of the pixel signal between the adjacent pixels is reduced by forming the trench between the respective pixels and forming the boundary portion 35 a having the same material (SiO2) as that of the oxidized film 35. Further, in place of the boundary portion 35 a, as illustrated in FIG. 12, a boundary portion 34 a having a metal, for example, W (tungsten) forming the light shielding film 34 may be formed.

Note that, in the solid-state imaging sensor 11 in FIG. 12, the same name and the same reference numeral are given to a configuration with the same function as that of the solid-state imaging sensor 11 in FIG. 1. A description thereof is omitted and is similar subsequently.

The solid-state imaging sensor 11 in FIG. 12 is different from the solid-state imaging sensor 11 in FIG. 1 in that, in place of the boundary portion 35 a, the boundary portion 34 a containing a metal is provided to be connected to the light shielding film 34. Thus, not only electrical isolation but also light shielding between adjacent pixels is possible. Therefore, the crosstalk can be prevented with higher precision.

<First Modification of Fifth Embodiment>

In the foregoing, the description has been given of the example in which the boundary portion 34 a is provided in a state of connection to the light shielding film 34. For example, the light shielding film 34 may not be provided but only the boundary portion 34 a may be provided.

That is, as illustrated in the solid-state imaging sensor 11 in FIG. 13, the light shielding film 34 may not be provided but the boundary portion 34 a may be provided.

With the configuration, the similar effect can be obtained by forming the boundary portion 34 a even in a state in which the light shielding film 34 is not provided.

<Sixth Embodiment>

In the foregoing, the description has been given of the general pixel for imaging. Further, application may be performed to, e.g., an image-plane phase difference focus pixel (ZAF pixel) that a part of pixels is light-shielded.

That is, on a part of the top surface of the pixel at the left end in the diagram, set as a ZAF pixel surrounded by a dotted line portion in the solid-state imaging sensor 11 in FIG. 14, the light shielding film 34 is formed. The boundary portion 35 a containing the similar material to that of the oxidized film 35 is also set by arranging a trench to the pixel with the unit basis of a pixel, thereby enabling suppression of not only the crosstalk between general pixels but also the crosstalk in the ZAF pixel. Note that, in the solid-state imaging sensor 11 in FIG. 14, a part of the ZAF pixel is light-shielded with the light shielding film 34. Therefore, the intermediate first layer 37 to reduce the reflection on the Si substrate 38 is not formed.

<First Modification of Sixth Embodiment>

In the foregoing, the description has been given of the example of arranging the boundary portion 35 a containing the same material as that of the oxidized film 35 between pixels. Further, similarly to the solid-state imaging sensor 11 in FIG. 12, in place of the boundary portion 35 a, the boundary portion 34 a containing the same material as the metal forming the light shielding film 34 may be provided between pixels.

That is, as illustrated by the solid-state imaging sensor 11 in FIG. 15, in place of the boundary portion 35 a, the boundary portion 34 a containing the same material as the metal forming the light shielding film 34 is provided between pixels.

With the configuration, it is possible to suppress not only the crosstalk between the general pixels but also the crosstalk in the ZAF pixel with higher precision.

<Second Modification of Sixth Embodiment>

In the foregoing, the description has been given of the example of arranging the boundary portion 34 a containing the same material as the metal forming the light shielding film 34 between pixels. Further, similar to the solid-state imaging sensor 11 in FIG. 13, the light shielding film 34 may not be provided, but only the boundary portion 34 a may be provided.

That is, as illustrated by the solid-state imaging sensor 11 in FIG. 16, the light shielding film 34 is not provided between pixels, but the boundary portion 34 a containing the same material as the metal forming the light shielding film 34 is provided therebetween.

With the configuration, it is possible to suppress not only the crosstalk between the general pixels but also the crosstalk in the ZAF pixel with higher precision.

<Third Modification of Sixth Embodiment>

In the foregoing, the description has been given of the example in which the intermediate first layer 37 is not formed to the image-plane phase difference focus pixel (ZAF pixel). Further, the intermediate first layer 37 may be also provided to the ZAF pixel.

That is, as illustrated by the solid-state imaging sensor 11 in FIG. 17, the intermediate first layer 37 is also formed to a pixel at the left end in the diagram, set as the ZAF pixel. It is also possible to suppress the reflection light on the Si substrate 38 in the ZAF pixel with the configuration, and perform focusing at higher speed with higher precision. Note that, although not illustrated, also in the solid-state imaging sensor 11 in FIG. 17, in place of the boundary portion 35 a, the boundary portion 34 a may be provided. Further, the light shielding film 34 is omitted and only the boundary portion 34 a may be provided.

<Examples of Application to Electronic Device>

The above-described solid-state imaging sensor can be applied to various electronic devices, for example, an imaging device such as a digital still camera and a digital video camera, a mobile phone having an imaging function, or other devices having an imaging function.

FIG. 18 is a block diagram illustrating a configuration example of an imaging device as an electronic device to which the present technology is applied.

An imaging device 201 illustrated in FIG. 18 includes an optical system 2202, a shutter device 203, a solid-state imaging sensor 204, a drive circuit 205, a signal processing circuit 206, a monitor 207 and a memory 208, and can image a still image and a moving image.

The optical system 202 includes one or a plurality of lenses, guides light (incident light) from a subject to the solid-state imaging sensor 204, and forms an image on a light receiving surface of the solid-state imaging sensor 204.

The shutter device 203 is disposed between the optical system 202 and the solid-state imaging sensor 204, and controls a light illumination period and a light-blocking period of the solid-state imaging sensor 204 under control of the drive circuit 205.

The solid-state imaging sensor 204 includes a package having the above-described solid-state imaging sensor. The solid-state imaging sensor 204 accumulates signal charges for a constant period according to light whose image is formed on a light receiving surface through the optical system 202 and the shutter device 203. The signal charges accumulated in the solid-state imaging sensor 504 are transferred according to a drive signal (a timing signal) supplied from the drive circuit 205.

The drive circuit 205 outputs a drive signal for controlling a transfer operation of the solid-state imaging sensor 204 and a shutter operation of the shutter device 203 and drives the solid-state imaging sensor 204 and the shutter device 203.

The signal processing circuit 206 performs various types of signal processing of signal charges output from the solid-state imaging sensor 204. An image (image data) obtained by signal processing performed by the signal processing circuit 206 is supplied to and displayed on the monitor 207, and is supplied to and stored (recorded) in the memory 208.

Also in the imaging device 201 with the configuration, in place of the solid-state imaging sensor 204, by applying the solid-state imaging sensor 11, the reflection on the Si substrate 38 can be suppressed to improve the sensitivity and reduce the flare and ghost.

<Use Examples of Solid-State Imaging Sensor>

FIG. 19 is a diagram illustrating use examples in which the above-described solid-state imaging sensor is used.

The above-described solid-state imaging sensor can be used for, for example, various cases in which light such as visible light, infrared light, ultraviolet light, or X-rays is detected as follows.

-   -   Devices that take images used for viewing, such as a digital         camera and a portable appliance with a camera function.     -   Devices used for traffic, such as an in-vehicle sensor that         takes images of the front and the back of a car, surroundings,         the inside of the car, and the like, a monitoring camera that         monitors travelling vehicles and roads, and a distance sensor         that measures distances between vehicles and the like, which are         used for safe driving (e.g., automatic stop), recognition of the         condition of a driver, and the like.     -   Devices used for home electrical appliances, such as a TV, a         refrigerator, and an air conditioner, to takes images of a         gesture of a user and perform appliance operation in accordance         with the gesture.     -   Devices used for medical care and health care, such as an         endoscope and a device that performs angiography by reception of         infrared light.     -   Devices used for security, such as a monitoring camera for crime         prevention and a camera for personal authentication.     -   Devices used for beauty care, such as skin measurement equipment         that takes images of the skin and a microscope that takes images         of the scalp.     -   Devices used for sports, such as an action camera and a wearable         camera for sports and the like.     -   Devices used for agriculture, such as a camera for monitoring         the condition of the field and crops.

Additionally, the present technology may also be configured as below.

(1)

A solid-state imaging sensor including:

a substrate having, per pixel unit, a photoelectric conversion unit configured to generate a pixel signal corresponding to an amount of incident light by photoelectric conversion;

a reflectance adjusting layer provided on the substrate in an incident direction of the incident light with respect to the substrate and configured to adjust reflection of the incident light on the substrate; and

an environmental medium provided on the reflectance adjusting layer, in which

the reflectance adjusting layer includes a first layer formed on the substrate and a second layer formed on the first layer,

the first layer includes a concavo-convex structure provided on the substrate and a material which is filled into a concave portion of the concavo-convex structure and has a refractive index lower than that of the substrate,

the second layer includes a material having a refractive index lower than that of the first layer, and

the refractive index of the substrate is higher than that of the first layer, the refractive index of the first layer is higher than that of the second layer, and the refractive index of the second layer is higher than that of the environmental medium.

(2)

The solid-state imaging sensor according to (1), in which

a product of the refractive index of the first layer and a thickness of the first layer is smaller than ⅜ times a wavelength of the incident light.

(3)

The solid-state imaging sensor according to (1), in which

the first layer includes a plurality of layers, and in a refractive index of each of the plurality of layers, and the refractive index of a layer closer to the substrate is higher among any adjacent layers,

in the case where a difference in the refractive index between the respective layers is higher than a predetermined value,

-   -   a product of the refractive index and the thickness is smaller         than ⅜ times the wavelength of the incident light in each of the         plurality of layers, and

in the case where the difference in the refractive indexes between the respective layers is lower than a predetermined value,

-   -   a sum of products of the refractive index and the thickness of         each of the plurality of layers is smaller than ⅜ times the         wavelength of the incident light.         (4)

The solid-state imaging sensor according to any one of (1) to (3), in which

a product of the refractive index of the second layer and a thickness of the second layer is smaller than ⅜ times the wavelength of the incident light.

(5)

The solid-state imaging sensor according to any one of (1) to (3), in which

the second layer includes a plurality of layers, and in a refractive index of each of the plurality of layers, the refractive index of a layer closer to the substrate is higher among any adjacent layers,

in the case where a difference in the refractive index between the respective layers is higher than a predetermined value,

-   -   a product of the refractive index and the thickness is smaller         than ⅜ times the wavelength of the incident light in each of the         plurality of layers, and

in the case where the difference in the refractive indexes between the respective layers is lower than a predetermined value,

-   -   a sum of products of the refractive index and the thickness of         each of the plurality of layers is smaller than ⅜ times the         wavelength of the incident light.         (6)

The solid-state imaging sensor according to any one of (1) to (5), in which

the refractive index of the first layer is a sum of products of volume ratios with the respective refractive indexes of a convex portion in the concavo-convex structure of the first layer including the same material as that of the substrate and the concave portion to which the material with the low refractive index is filled.

(7)

The solid-state imaging sensor according to any one of (1) to (6), in which

the substrate includes Si and InGaAs, a material filled into a concave portion of the first layer includes an oxidized film or a nitride film containing at least one kind of Hf, Al, Ti, Zr, Ta, Nb, Y, and Sr, and the environmental medium includes a lens, a color filter, and an oxidized film.

(8)

The solid-state imaging sensor according to (7), in which a material filled into the concave portion of the first layer includes SiN, HfO2, Ta2O5, Nb2O5, TiO2, Al2O3, and ZrO2.

(9)

The solid-state imaging sensor according to any one of (1) to (8), in which

a material filled into the concave portion of the first layer is the same material as that of the second layer.

(10)

The solid-state imaging sensor according to any one of (1) to (9), in which

a material filled into the concave portion of the first layer is the material with high dielectric constant.

(11)

The solid-state imaging sensor according to any one of (1) to (10), in which

the concavo-convex structure provided on the substrate is configured by using photolithography or etching using directed self assembly (DSA).

(12)

The solid-state imaging sensor according to any one of (1) to (11), in which

a boundary per the pixel unit includes an oxidized-film boundary portion including an oxidized film.

(13)

The solid-state imaging sensor according to (12), in which

the pixel includes an image-plane phase difference focus pixel.

(14)

The solid-state imaging sensor according to any one of (1) to (13), in which

a boundary per the pixel unit includes a metallic boundary portion including a metal.

(15)

The solid-state imaging sensor according to (14), in which

the metal includes tungsten.

(16)

The solid-state imaging sensor according to (14), in which

the pixel includes an image-plane phase difference focus pixel.

(17)

The solid-state imaging sensor according to (14), in which:

a light shielding unit which is the boundary per the pixel unit and which includes the same metal as that of the metallic boundary portion and shields the incident light onto an adjacent pixel to surround the pixel in a direction facing to an incident direction of the incident light.

(18)

The solid-state imaging sensor according to (17), in which

the pixel includes an image-plane phase difference focus pixel.

REFERENCE SIGNS LIST

-   11 solid-state imaging sensor -   31 lens -   32 color filter -   33 planarized film -   34 light shielding film -   34 a boundary portion -   35 oxidized film -   35 a boundary portion -   36, 36-1, 36-2 intermediate second layer -   36 a boundary portion -   37, 37-1, 37-2 intermediate first layer -   37 a, 37 a′ concave portion -   38 Si substrate 

The invention claimed is:
 1. A solid-state imaging sensor, comprising: a plurality of pixel units; a substrate including a photoelectric conversion unit for each pixel unit of the plurality of pixel units, wherein the photoelectric conversion unit is configured to generate a pixel signal corresponding to an amount of incident light by photoelectric conversion; a reflectance adjusting layer on the substrate in an incident direction of the incident light with respect to the substrate, wherein the reflectance adjusting layer is configured to adjust reflection of the incident light on the substrate; and an environmental medium on the reflectance adjusting layer, wherein the reflectance adjusting layer includes a first layer on the substrate and a second layer on the first layer, the first layer includes a concavo-convex structure on the substrate, wherein a concave portion of the concavo-convex structure includes a first material, and wherein each of a convex portion of the concavo-convex structure and the substrate include a second material, a first refractive index of the first layer is lower than a second refractive index of the substrate, the second layer includes the first material having a third refractive index lower than the first refractive index, and the third refractive index is higher than a fourth refractive index of the environmental medium.
 2. The solid-state imaging sensor according to claim 1, wherein a product of the first refractive index and a thickness of the first layer is smaller than 3/8 times a wavelength of the incident light.
 3. The solid-state imaging sensor according to claim 1, wherein the first layer includes a plurality of sub-layers, a fifth refractive index of a first sub-layer of the plurality of sub-layers is highest among refractive indices of sub-layers of the plurality of sub-layers other than the first sub-layer, based on a difference, in respective refractive indices between two adjacent sub-layers of the plurality of sub-layers, that is higher than a threshold value, a first product of the difference and a thickness of the two adjacent sub-layers is smaller than 3/8 times a wavelength of the incident light for each layer of the plurality of sub-layers, and based on the difference that is lower than the threshold value, a sum of products of a respective refractive index and a respective thickness of each of the plurality of sub-layers is smaller than 3/8 times the wavelength of the incident light.
 4. The solid-state imaging sensor according to claim 1, wherein a product of the third refractive index and a thickness of the second layer is smaller than 3/8 times a wavelength of the incident light.
 5. The solid-state imaging sensor according to claim 1, wherein the second layer includes a plurality of sub-layers, a fifth refractive index of a first sub-layer of the plurality of sub-layers is highest among refractive indices of sub-layers of the plurality of sub-layers other than the first sub-layer, based on a difference, in respective refractive indices between two adjacent sub-layers of the plurality of sub-layers, that is higher than a threshold value, a first product of the difference and a thickness of the two adjacent sub-layers is smaller than 3/8 times a wavelength of the incident light for each layer of the plurality of sub-layers, and based on the difference that is lower than the threshold value, a sum of products of a respective refractive index and a respective thickness of each of the plurality of sub-layers is smaller than 3/8 times the wavelength of the incident light.
 6. The solid-state imaging sensor according to claim 1, wherein the first refractive index is a sum of products of volume ratios with respective refractive indices of a plurality of convex portions in the concavo-convex structure of the first layer, and wherein the plurality of convex portions include the convex portion.
 7. The solid-state imaging sensor according to claim 1, wherein the substrate includes Si and InGaAs, the first material includes a first oxidized film or a nitride film of at least one of Hf, Al, Ti, Zr, Ta, Nb, Y, and Sr, and the environmental medium includes a lens, a color filter, and a second oxidized film.
 8. The solid-state imaging sensor according to claim 7, wherein the first material further includes SiN, HfO₂, Ta₂O₅, Nb₂O₅, TiO2, Al₂O₃, and ZrO₂.
 9. The solid-state imaging sensor according to claim 1, wherein each of the concave portion of the first layer and the second layer includes the first material.
 10. The solid-state imaging sensor according to claim 1, wherein a dielectric constant of the first material is higher than a threshold value.
 11. The solid-state imaging sensor according to claim 1, wherein the concavo-convex structure on the substrate is configured by one of photolithography or directed self assembly (DSA).
 12. The solid-state imaging sensor according to claim 1, wherein a boundary of the each pixel unit of the plurality of pixel units includes an oxidized-film boundary portion, and wherein the oxidized-film boundary portion includes an oxidized film.
 13. The solid-state imaging sensor according to claim 12, wherein the each pixel unit of the plurality of pixel units includes an image-plane phase difference focus pixel.
 14. The solid-state imaging sensor according to claim 1, wherein a boundary of the each pixel unit of the plurality of pixel units includes a metallic boundary portion, and wherein the metallic boundary portion includes a metal.
 15. The solid-state imaging sensor according to claim 14, wherein the metal is tungsten.
 16. The solid-state imaging sensor according to claim 14, wherein the each pixel unit of the plurality of pixel units includes an image-plane phase difference focus pixel.
 17. The solid-state imaging sensor according to claim 14, further comprising a light shielding unit as the boundary, wherein the light shielding unit includes the metal of the metallic boundary portion, wherein the light shielding unit is configured to surround a first pixel unit of the plurality of pixel units in a direction opposite to the incident direction of the incident light, and wherein the light shielding unit is further configured to shield the incident light onto a second pixel unit of the plurality of pixel units, wherein the second pixel unit is adjacent to the first pixel unit.
 18. The solid-state imaging sensor according to claim 17, wherein the each pixel unit of the plurality of pixel units includes an image-plane phase difference focus pixel.
 19. A solid-state imaging sensor, comprising: a plurality of pixel units; a substrate including a photoelectric conversion unit for each pixel unit of the plurality of pixel units, wherein the photoelectric conversion unit is configured to generate, a pixel signal corresponding to an amount of incident light by photoelectric conversion; a reflectance adjusting layer on the substrate in an incident direction of the incident light with respect to the substrate, wherein the reflectance adjusting layer is configured to adjust reflection of the incident light on the substrate; and an environmental medium on the reflectance adjusting layer, wherein the reflectance adjusting layer includes a first layer in direct contact with the substrate and a second layer on the first layer, the first layer includes a concavo-convex structure on the substrate, wherein a concave portion of the concavo-convex structure includes a first material, and wherein each of a convex portion of the concavo-convex structure and the substrate include a second material, a first refractive index of the first layer is lower than a second refractive index of the substrate, the second layer includes the first material having a third refractive index lower than the first refractive index, the third refractive index is higher than a fourth refractive index of the environmental medium, and the first refractive index is a sum of products of volume ratios with respective refractive indices of convex portions in the concavo-convex structure of the first layer. 